Present day commercial oilseed processing techniques emphasize the production of bright, superdegummed oil and result in the removal from the oil of gums, soapstocks, bleaching clays and pigments, which are by-product materials and which are disposed of by adding them back to the meal resulting from crushing the oil seeds to remove the oil.
The addition of such materials to the oil seed meal results in a situation where it is not possible to extract protein isolates containing in excess of about 90% protein from such meals using environmentally sensitive isolation techniques. The fat present in the commercial meals normally results in concentration of the fat along with the protein in conventional processing techniques.
Protein levels which can be achieved with conventional processing techniques generally do not exceed about 70 to 75 wt % and their functionality in food systems is impaired by virtue of the interference of the fat. In addition, the presence of the fat in the dry protein product can lead to rancidity and other fat-related problems, including poor solubility, caking etc., as well as discoloration resulting from co-processing of pigments in the meal with the fat.
One emphasis of oil seed plant breeding program is towards improving the yield of oil from the oil seeds and indeed cultivars have been developed, for example, for canola (rapeseed) which are higher yielding in term of oil. However, such enhanced oil production has the effect of increasing the proportion of fat which is present in the oil seed meal as a result of the addition of the by-products from the oil refining to the oil seed meal.
While it is possible to at least partially remove such fats from the oil seed meals by extraction with organic solvents, the use of organic solvents, especially at elevated temperatures, tends to denature the protein, thereby impairing the functionality of the product, and, in addition, gives rise to a disposal and recovery problem that is not environmentally responsible.
In U.S. Pat. No. 4,208,323, of which I am an inventor, there is described a process for the isolation of proteins from various sources. The protein source materials which are employed in such process may come from a variety of sources, including oil seeds. The oil seed meals which were available in 1980, at the time of the issuance of the patent, did not have the fat contamination levels which are present in current oil seed meals and, as a consequence, the process that is described in the earlier patent, cannot produce from the present-day oil seed meals, proteinaceous material products which have the more than 90% protein content, which is a property of the proteinaceous materials produced by the process produced in the patent. It is necessary to employ a significant modification to such process to enable such products to be produced from present-day oil seed meals, including cold-pressed meals.